The present invention relates generally to information storage devices. More particularly, the present invention relates to information storage devices including energy beam sources such as, but not limited to, electron emitters and near-field optical sources.
For decades, researchers have been working to increase storage density and reduce storage cost of information storage devices such as magnetic hard-drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult. Conventional technologies appear to be approaching fundamental limits on storage density. For instance, information storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, below which a magnetic bit is not stable at room temperature.
Information storage devices that do not face these fundamental limits are being researched. One such device, an ultra-high density information storage device, includes multiple electron emitters having electron emission surfaces that are proximate a storage medium. During a write operation, an electron emitter changes the state of a submicron-sized storage area on the storage medium by bombarding the storage area with a relatively high intensity electron beam having an appropriate pulse shape and amplitude. If the storage medium is based upon a phase-change material, the storage area might be changed from a crystalline state to an amorphous state or vice-versa. By changing the state of the storage area, a bit is written to the storage area.
During a read operation on a storage area, an electron emitter bombards the storage area with an electron beam. A resulting signal is detected to determine the state of that storage area. The electron beam used for read operations can be of a relatively low intensity so as not to change the state of the storage area.
According to one aspect of the present invention, a storage area is located within a region between two electrodes in contact with a cathodoconductive medium. A state of the storage area is read by generating an electric field across the region between the electrodes; bombarding the storage area with an energy beam; and monitoring the magnitude of a current flowing between the electrodes.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.